Colorectal cancer is a common malignant tumor, and the third lethal tumor in the world. In the developed western countries, colorectal cancer gets morbidity at second place following lung cancer. In China, the morbidity and mortality of colorectal cancer also show an ascending trend from the sixth place in 1980s to the fourth place at present.
Targeted therapy of tumors is a newly developed method for treatment of cancers, which avoid to a great extent in spread of tumors and serious toxic and side-effects caused by conventional cancer therapies such as operative treatment, chemotherapy and radiotherapy. Monoclonal antibody therapy aiming at tumor cell surface antigens is a main targeted therapy for tumors and exhibits good oncotherapy effects.
Cellular prion protein (PrPc) is a glycoprotein widely expressed on surface of eukaryotic cells, which has 253 amino acids, a glycosylphosphatidylinositol (GPI) binding site at C-terminal for docking at outer membrane of cells, and two aspartate residues at sites 181 and 197 as glycosylation sites. In a mammal, PrPc is mainly expressed in nervous system, but also expressed in non-neural tissues such as lymphocytes, gastric epithelial cells, kidney cells, and muscles. In some reports, PrPc relates to tumorigenesis and drug-resistance, and it is highly expressed in cancer tissues of many cancers such as colorectal cancer, prostate cancer, gastric cancer, etc. The preliminary work of the present invention also shows that the cells with co-expression of CD44 and PrPc have features of tumor stem cells. In addition, some reports state that PrPc also plays an important role in hepatic metastases of colorectal cancer stem cells. Hence, researches of targeted therapy aiming at PrPc on the basis of monoclonal antibody are promising in providing a new therapy for cancer treatments.